Passenger and freight.
However, here are a couple of first-hand observations:
- I recall seeing the Prospector depart Salt Lake City in 1961 behind a FTA-FTB-F3B-F3A in fresh, single-stripe, paint and black roofs. I always associated the silver roof with the bumblebee style paint (early 1950's through early 1960's), and then only on passenger engines.
- Also on that 1961 trip, the Yampa Valley Mail making daily stops at Steamboat Springs behind an Alco-GE PA1 in new single stripe paint and a black roof.